Reading the script, Van Dyke found the role of the senior, crotchety bank president so hysterical, he lobbied for the second part, even offering to play Mr. Dawes Sr. for free, the actor told CNN. Disney not only made him audition, in full makeup, for the role but also forced the actor to make a $4,000 donation to the California Institute of the Arts, the private arts university Disney founded. (“The CalArts Story” was first presented at the premiere of “Mary Poppins” and can be seen at calarts.edu/about/history.)

Years later when Van Dyke saw the theater adaptation of “Mary Poppins,” he volunteered to join the Los Angeles cast for one performance and reprise his role as Mr. Dawes Sr. The character is not included in the stage version but was written into a scene so Van Dyke could make a surprise cameo, the website Playbill.com reported. Now 84, he was old enough to play the stage character Disney considered him too young to play in the movie.

Because “Saving Mr. Banks” is not a documentary, there are discrepancies historians familiar with the actual production history of "Mary Poppins" will recognize.

“Saving Mr. Banks” indicates that Disney was working at the studio during Travers’ entire Los Angeles visit. But in reality, according to the website DisneyD55.com, once he recognized how difficult she was to work with, Disney left town for an unscheduled Palm Springs vacation. He also never visited her London home.

In “Saving Mr. Banks,” Travers and Disney eventually become firm friends, with the author being won over to enjoy "Mary Poppins" and applaud at its premiere. Wrong! “Saving Mr. Banks” director John Lee Hancock explained in an article written by Susan Wloszczyna on rogerebert.com, "We know Travers was not invited to the premiere. She invited herself. She did not care for the movie. She went to Walt afterward and said we have some work to do and he told her, 'That ship has sailed.'"

Travers remained so antagonistic toward the film that when "Mary Poppins" went to Broadway, she stipulated that no Americans of any stripe be involved. Robert B. and Richard M. Sherman — the composer team who contributed so mightily to the film's success, with “Mary Poppins” earning the brothers their only two Oscars — were shut out from writing the necessary additional songs.

According to the book “Hello Goodbye Hello,” seeing the "Mary Poppins" film was “an emotional shock which left me deeply disturbed,” Travers had said.